As I write this on Thursday night, a powerful storm is forming in the western Pacific near Japan. Cold air from East Asia moving over the warm waters of the Kuroshio Current is causing rapid storm development. This is enhanced by moisture from two decaying typhoons, Mitag and Hagibis, which have moved into the mid-latitudes. Everything is setting up for a big West Coast event.

The predictive models are beginning to come together in agreement regarding what comes next. They are suggesting that, by tonight, strong winds will begin to affect the Oregon coast. Monday and Monday night look rather windy in the inland valleys.

And then the rains are expected to arrive. The storm will be tapping copious amounts of subtropical moisture, producing an "atmospheric river," the type of condition that gives us our wettest rain events. Because of its original tropical location, the "river" is a very warm one, and high freezing levels are expected. A "rain on snow" event, caused by a combination of melted snow and heavy rain, might occur. We may get a big windstorm followed by a big flood. It's still too early to tell, but by the time you read this, we'll have a better idea.

The storm will kick up some pretty big surf as well. The U.S. Navy wave model is predicting 25- to 30-foot waves for our coastline early next week.

And just how big a windstorm will we have? According to the National Weather Service, the kid of storm we get about once every five to 10 years. In other words, BIG! In fact, this storm has caused NWS officials to issue a wind warning that they have never used before.

In 2002, NWS received a directive that gave forecast offices the authority to issue a hurricane force wind warning in the marine forecast. According to Bill Schneider of the Portland NWS office, the purpose is to highlight the extreme nature of rare storms that may occur only once every five to 10 years.

Mind you, these are not actually hurricanes, which are tropical storms. Rather, this type of storm is an "extratropical cyclone," a storm formed and sustained by an intersection of warm and cold air. Tropical storms have just warm air. Extratropical cyclones are much larger than hurricanes and thus have much broader impact zones.

Schneider went on, "The current threat appears to be mostly to the water and the immediate coastline. This storm has the potential to damage ships or cargo and will be difficult to avoid because of the huge area it will cover." Thus, the first-ever hurricane-force wind warning in the Northwest was issued.

Shades of 1962, when a dying typhoon moved into the North Pacific, regained strength and turned into the Columbus Day Storm, the most powerful storm to hit the Northwest on record. That storm had winds comparable to a Category 3 or 4 hurricane.

We probably won't get anything like that, but just to be safe, be sure you're prepared for possible power failures. Big wind and big water is a bad combination!

George Taylor directs the Oregon Climate Service at Oregon State University. He can be reached at 737-5705 or taylor@coas.oregonstate.edu.